1. Field of the Invention
This invention relates to an actuation system for multi-section devices, such as self-contained ramps and ladders mounted within transport vehicles for providing loading and unloading of cargo and passengers when the vehicle is stationary.
2. Description of the Prior Art
It has long been known to provide a multi-section ramp or stairway assembly which can be wholly contained within a transportation vessel or vehicle such as an airplane or a ship. U.S. Pat. No. 2,933,149 of Lee, representative of known prior art in this field, discloses a self-contained stair unit for extension from an aircraft by means of a series of linkages and levers. Such units as are known typically involve rotation in both the clockwise and counterclockwise direction about various axes of rotation along the extended, articulated stair assembly. It has also been known before to actuate the extension and retraction of the stairway assembly by the movement of a cable attached to pulleys which are capable of rotating the articulated assembly as desired by means of various mechanical linkages. A cable assembly actuating arrangement representative of the prior art is seen in U.S. Pat. No. 2,531,263 of Fink et al. Another representative patent showing such cable actuation of the rotation of the various sections of the stairway assembly about respective axes of rotation can be seen in U.S. Pat. No. 3,083,784 of Uriah. In such arrangements, it is characteristic that the assembly will fold or unfold in zigzag fashion by rotating about adjacent axes of rotation in opposite directions.